Carbon Copy – An e-mail message which is sent to another address apart from the principal.

CD audio – content of a musical CD.

CGI - (Common Gateway Interface) Encrypted program for interface development which enables fast creation of www pages. It is based on filling in forms, frames, text insertion etc.

Client – As opposed to client-server, client is a computer which opens programs or application from the server or takes files from it.

Clip art – A collection of images delivered on a CD-ROM which can be inserted into a document.

CODEC – Short for coder-decoder; a device which converts analogue sound signal into a digital sequence of bits and vice versa. It uses impulse modulation for this purpose.

Compiler – in the multimedia context a compiler is professional software component which creates a title by translating commands written by a programmer.

Compress – The process of removing unnecessary or partly unnecessary information from a file, making it smaller for easier storage.

Compression – Processing of a file, such as a sound file, in order to reduce its size for storing on a disk.

Compression – Compression i.e. diminishing the quantity of digital data based on discarding the data which is not essential for the quality of a video or audio file. Human eye and ear do not notice the lack of these data. Part of the video signal which is repeated several times is transferred only once. A similar thing happens with sound. Sound segments which the human ear cannot hear are discarded. This reduces the quantity of data that needs to be stored and transferred.
- Compression was initially intended only when a digital signal is being transferred. However, nowadays it is also used for storing digital video signals on computers and recording onto CDs or DVDs. By using compressions the necessary capacity of the storage medium are reduced.
- Signal distortions caused by compression may happen during the compression process. Such distortion occur if strong compression is being done. It is then that certain irregularities in the decompressed signal may occur. Distortions manifest as noise, there are often distorted picture areas or the picture can disappear altogether, especially pictures which contain faster movements.